During the stamp charging process the coal is compacted outside the coke oven, into a stable "briquette“ (coal cake) with almost the same dimensions as the oven chamber and the resulting cake is pushed into the oven.  With stamp charging the bulk density of the charge is increased between 30 to 35% (a 45% increase is reported in Veit & D'Lama, 2002) and the productivity of the oven is increased between 10-12% (up to 28% increase in capacity can be obtained (Veit & D'Lama, 2002)).  In addition, the technology allows for using lower quality coking coal and improves the quality of the produced coke.